Buying a used car with a replaced transmission?

Ive been looking for a used car for awhile now (preferably Toyota) and have come down to two choices: 2001 Toyota Celica. Both of my choices are the same model and year and both from private sellers. Both cars a roughly the same mileage (132,000 and 148,000.) My observation is that on the 148,000mile car ad the owner states that his has a new transmission. Would that be a better choice than the 132,000mile car? I know to ask the 148 owner where he had his transmission replaced and why, but is there anything i can ask for proof? A receipt or inspection paper? I am wanting information on this because im narrowing down my choice of cars to one for I have to fly upstate 500+ and i need to be as sure as possible for what im going to buy so i can drive it back downstate.